The present invention relates to a new and improved method and apparatus for production of a yarn or the like by means of friction spinning equipment or friction spinning means.
Generally speaking, the inventive method for the production of a yarn or the like by friction spinning means contemplates separating the fibers from a body of fibers and such separated fibers are transferred to the friction spinning means to form a spun yarn, and this spun yarn is withdrawn in a direction defined or governed by the friction spinning means.
The apparatus of the present invention for the production of a yarn or the like comprises means for delivering fibers from a body of fibers, friction spinning means for receiving or taking-up the delivered fibers and for forming therefrom a spun yarn, and means for withdrawing the spun yarn.
Friction spinning is a spinning process in which fibers are separated from a fiber body, delivered to a moving perforated surface and twisted together thereon to form a spun yarn. A suction air stream passes through the moving perforated surface in a predetermined region or zone thereof, so that the fibers delivered to this predetermined region of the moving perforated surface are entrained in the suction air stream, moved onto the moving perforated surface, transported thereon to the end of this predetermined region, as viewed in the direction of movement of the moving perforated surface, and are thereafter twisted into a yarn. Twisting-in of the fibers is caused by the portion of the air stream or flow which, in this end region of the air stream or flow, is directed opposite to the direction of movement of the moving perforated surface and which thus catches fibers lying on the moving perforated surface and continually twists them into the yarn.
Due to the continuous withdrawal of the twisted fibers, which withdrawal also constitutes an aspect of the aforementioned friction spinning process, a spun yarn is produced with true twist.
From German Published Pat. No. 1,902,111, published Sept. 4, 1969, there is known to the art both a method and an apparatus by means of which a yarn of the type mentioned above is produced.
In this prior art method, fibers are separated by a toothed roller from a body of fibers and are transferred to an air stream passing around this toothed roller. In this air stream, the fibers are turned from a position oriented in the peripheral direction of the toothed roller into a position oriented substantially parallel to the axis of rotation of such toothed roller. After these fibers have reached the aforementioned position which is disposed parallel to the axis of rotation of the toothed roller, they are transferred to a suction drum. On the surface of this suction drum the fibers are transported, while still in a position disposed substantially parallel to the axis of rotation of the suction drum, to the previously described end or boundary region of such a suction air stream or flow, and, as likewise previously described, are twisted together and withdrawn by appropriate withdrawal means as a spun yarn. Twisting of the fibers into the yarn is assisted by an additional roller or roll extending parallel to the suction drum and almost contacting the suction drum. Accordingly, the directions of movement of the two last-mentioned rollers or rolls are opposite to one another at their region of closest approach, that is to say, the directions of rotation of both rollers or rolls are the same.
It is a considerable disadvantage of this prior art method that the fibers experience a change of direction, which is caused by the air flow, at the periphery of the toothed roller; this can be effected only with inadequate regularity. As a result, the fibers are placed in dissimilar or irregular positions on the subsequently arranged suction drum, and thus they also have an uneven density. This uneven or irregular density produces undesired unevenness in the yarn, especially if the processed fibers have a relatively short staple length, for example as experienced in cotton spinning.
Also from the German Published Pat. No. 2,943,063 it is known to the art to separate fibers from a body of fibers by means of a drum equipped with clothing having teeth or needles, and to transfer the fibers to an air stream. At the end of this air stream, the fibers are delivered into the converging space of two drums rotating with the same rotational direction, where the fibers are then twisted together and withdrawn as yarn. One of the two drums is a perforated suction drum in order to provide the fibers with the previously mentioned possibility of twisting in of the fibers.
The disadvantage of this prior art method and apparatus is that upon their arrival in the converging space the fibers must be decelerated from the high transport speed in the air stream practically to zero speed. This fiber deceleration can lead to longitudinal compression of the fibers and therefore to a non-drawn-out condition of the fibers in the yarn.